1. Field of the Invention
The present invention relates to a heat-resistant rubber hose for a diesel engine for use as a diesel particulate filter (DPF) sensor hose, a vacuum brake hose, an air hose, a turbo (supercharger) air hose and the like for a diesel engine.
2. Description of the Related Art
With increasing worldwide environmental awareness, DPF systems and turbo systems have been positively employed for reducing PM (particulate matter) and NOx in exhaust gas. Conventionally, hoses each configured such that an inner layer thereof to be kept in contact with fuel is formed of a fluororubber or an acrylic rubber are proposed for use as fuel hoses and air hoses (see, for example, JP-A-7 (1995)-229584 and JP-A-2003-82029).
In recent years, emission control for diesel-powered vehicles has been tightened. To cope with this, new engine systems (e.g., common-rail injection systems), and DPF systems and turbo systems for the reduction of PM and NOx in the exhaust gas have been positively employed. Under such circumstances, stricter performance requirements are imposed on heat-resistant rubber hoses such as DPF sensor hoses for diesel engines. More specifically, where combustion efficiency is increased for the reduction of PM and NOx in the exhaust gas, the DPF system and the turbo system are subjected to elevated temperatures. Therefore, the heat-resistant rubber hoses are required to be more excellent in heat resistance, acid resistance, flame resistance and low-temperature property than conventional hoses. However, a conventional hose having an inner layer of a fluororubber (FKM) contains an acid acceptor (a metal salt such as magnesium oxide, zinc oxide or calcium oxide) and, therefore, is inferior in resistance to exhaust gas water (acid resistance). A conventional hose having an outer layer of an epichlorohydrin-ethylene oxide copolymer (ECO) is insufficient in heat resistance. Further, a conventional hose having inner and outer layers of an acrylic rubber (ACM) essentially requires a post cure process, so that the outer layer thereof has poorer flame resistance.
In view of the foregoing, it is an object of the present invention to provide a heat-resistant rubber hose for a diesel engine, which is excellent in exhaust gas water resistance (acid resistance), heat resistance, flame resistance and low-temperature property.